Protective circuit for a motor

ABSTRACT

A protective circuit for a motor comprises a rotational unit; a drive unit and a control unit. The drive unit is connected to the rotational unit to drive the rotational unit in running. The control unit is connected to the drive unit to control output or drive current of the drive unit. The rotational unit and the drive unit do not occur high temperature due to excessive drive current such that damage can be avoided. The control unit is a comparator or an operation amplifier connecting with at least a comparison circuit composed of a capacitor and a plurality of resistors to generate control signal.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention is related to a protective circuit for a motor and particularly to a comparison unit associated with a drive unit controlling instantaneous pulse current and voltage produced during the motor being started and drove by the drive unit to avoid occurring high temperature of the motor and the drive unit and resulting in damage.

2. Brief Description of the Related Art

Usually, coil sets in a motor produce a phenomenon of sparkling resulting from instantaneous high pulse once the motor is powered on. Referring to FIG. 1, a conventional circuit comprises a motor 11, which at least includes a first coil set 110 and a second coil set 120, a drive unit 20, which at least includes a drive IC 210 and a Hall element 220. The drive unit 20 is connected to the motor 11. The Hall element 220 senses magnetic pole change of the rotor in the motor 11 to produce positive voltage H+ and negative voltage H−outputs and the positive and negative voltages H+ and H− outputs are connected to corresponding H+ pin 2109 and H− pin 2111 of the drive IC 210. The first output pin 2115 is connected to the first coil set 110 and second output pin 2101 of the drive IC 210 is connected to the second coil set so that the motor 11 can be actuated to run. However, an instantaneous high pulse current and voltage are produced while the first coil set 110 and the second coil set 120 in the motor 11 is powered on to start the motor. Under this circumstance, the temperature of the drive IC 210 and the motor 10 rises quickly and it leads to the drive IC 210 and the motor 10 become damage.

SUMMARY OF THE INVENTION

A primary object of the present invention is to provide a protective circuit of a motor, which can avoid instantaneous high pulse current and voltage while the motor is started, not only to reduce the temperature of the motor but also to avoid temperature sudden rise of the drive member such that life span of the drive member and the motor can be prolonged.

Another object of the present invention is to provide a protective circuit of a motor, which can save energy due to the drive current for driving the motor being less.

A protective circuit of the present invention at least comprises a rotational unit, a drive unit connected to the rotational unit for driving the rotational unit, a control unit being connected to the drive unit to control output or driving current of the drive unit for starting and driving the rotational unit such as the motor to prevent from high temperature due to being excessively high pulse so as to reduce power consumption and prolong life span of the drive unit or the rotational unit. The control unit can be a comparison circuit composed of a comparator or an operation amplifier being connected to at least a capacitor and a plurality of resistors.

BRIEF DESCRIPTION OF THE DRAWINGS

The detail structure, the applied principle, the function and the effectiveness of the present invention can be more fully understood with reference to the following description and accompanying drawings, in which:

FIG. 1 is a conventional protective circuit diagram of a motor;

FIG. 2 is a block diagram of protective circuit for a motor according to the present invention in a preferred embodiment; and

FIG. 3 is a diagram of protective circuit for a motor according to the present invention in a preferred embodiment thereof.

DETAILED DESCRIPTION OF THE INVENTION

Referring to FIG. 2, a block diagram of protective circuit for a motor according to the present invention at least includes a rotational unit 10, a driving unit 20 connected to the rotational unit 10 to actuate the rotational unit 10 and a control unit 30 connected to the driving unit 20 to control output or driving current of the driving unit 20.

Referring to FIG. 3 in company with FIG. 2, the rotational unit 10 at least includes a first coil set 110 and a second coil set 120. The driving unit 20 at least includes a drive IC 210 and a Hall element 220 and the Hall element 220 senses magnetic pole change of the rotor in the rotational unit 10 to create positive voltage H+ and negative voltage H− outputs connected to corresponding H+ pin 2109 and H− pin 2111 on the drive IC respectively. The first output pin 2115 of the drive IC 210 is connected to the first coil set 110 and the second output pin 2101 of the drive IC 210 is connected to the second coil set 120 such that the rotational unit 10 can be actuated to run. The rotational unit 10 can be a motor.

The control unit 30 at least includes a comparator (or an operation amplifier) 310 and the positive phase input end 3101 of the comparator 310 is connected to a CT pin 2113 of the drive unit 20. The positive phase input end 3101 further parallel connects with a capacitor C1. The negative input end 3102 of the comparator 310 connects with a resistor R5 and another resistor R6 with an end of the resistor R5 not connecting with the negative input end 3102 is inputted DC power and an end of the resistor R6 not connecting with the negative input end 3102 is grounded. That is, the negative phase input end 3102 of the comparator 310 receives branch voltage signal composed of the resistors R5, R6.

When the rotational unit 10 stops running, the Hall element 220 is incapable of sensing the magnetic pole change of the rotor in the rotational unit 10 such that it is unable to produce positive voltage H+ and negative voltage H− outputting to the drive unit 20. Under this circumstance, CT pin 2113 of the drive unit 20 can produce a signal such as pulse wave or square wave to allow the capacitor C1 parallel connected to the positive input end 3101 of the comparator 310 receiving signal from CT pin 2113 and performing charge and discharge. After CT pin 2113 being charged, the positive phase input end 3101 connected to CT pin 2113 produces a high reference level signal in case of the voltage at the positive phase input end 3101 being greater than the branch voltage composed of the resistors R5, R6 and received by the negative phase input end 3102.

The comparator 310 at the output end 3103 thereof connects with an end of the resistor R4 and another end of the resistor R4 connects with an end of a resistor R3 and another end of the resistor R3 is grounded. That is, the resistors R4 and R3 result in the high reference signal at the output end 3103 of the comparator 310 producing voltage divide. Further, the resistors R4 and R5 has series connecting end to connect VTH pin 2105. That is, the VTH pin 2105 receives the divide voltage signal of the resistor R3.

When the VTH pin 2105 receives positive phase signal, output current of both of the first output pin 2115 and the second output pin 2102 of the drive unit 20 is restricted in case of the divide voltage of the resistor R3 is positive (greater than 0) such that the deficiency of the conventional art being easy to produce an instantaneous high voltage and voltage pulse, which lead to temperature rise quickly, during starting a motor can be overcome by way of controlling or reducing current which drives the first coil set 110 and the second coil set 120 of the rotational unit 10. Further, it can reduce waste of the power source.

In an alternative embodiment, in case of the rotational unit 10 being in a state of stop running continuously, the driving unit 20 drives the rotational unit 10 intermittently such that the conventional art is more easier to accumulate the heat quickly so as to result in temperature rise abruptly, which is apt to damage the rotational unit 10 and the driving unit 20. The protective circuit for a motor according to the present invention can reduce or control the current driving the first coil set 110 and the second coil set 120 of the rotational unit 10 such that rotational unit 10 or driving unit 20 can rise the temperature with a speed corresponding to the heat dissipation speed to avoid overheat and burn-out.

It is appreciated that the protective circuit for a motor according to the present invention is capable of reducing drive current of the rotational unit 10 substantively to save the power source. The temperature of the drive IC 210 and the rotational unit 10 according to the present invention can maintain in a steady state by way of controlling the drive current instead of high current and high voltage pulse resulting in heat accumulation speedily to occur phenomenon of high temperature so that life span of the motor can be prolonged effectively.

While the invention has been described with referencing to a preferred embodiment thereof, it is to be understood that modifications or variations may be easily made without departing from the spirit of this invention, which is defined by the appended claims. 

1. A protective circuit for a motor, comprising: a rotational unit; a drive unit, being connected to the rotational unit to drive the rotational unit in running; and a control unit, being connected to the drive unit to control output or drive current of the drive unit.
 2. The protective circuit for a motor as defined in claim 1, wherein the rotational unit is the motor.
 3. The protective circuit for a motor as defined in claim 1, wherein the drive unit at least comprises a drive IC and a Hall element.
 4. The protective circuit for a motor as defined in claim 1, wherein the control unit at least comprises a comparator.
 5. The protective circuit for a motor as defined in claim 4, wherein the comparator comprises a positive phase input end.
 6. The protective circuit for a motor as defined in claim 4, wherein the comparator comprises a negative phase input end.
 7. The protective circuit for a motor as defined in claim 5, wherein the comparator at least comprises an output end.
 8. The protective circuit for a motor as defined in claim 6, wherein the comparator at least comprises an output end.
 9. The protective circuit for a motor as defined in claim 5, wherein the positive phase input end at least connects with a capacitor in parallel.
 10. The protective circuit for a motor as defined in claim 6, wherein the positive phase input end at least connects with a capacitor in parallel.
 11. The protective circuit for a motor as defined in claim 7, wherein the positive phase input end at least connects with a capacitor in parallel.
 12. The protective circuit for a motor as defined in claim 8, wherein the positive phase input end at least connects with a capacitor in parallel.
 13. The protective circuit for a motor as defined in claim 9, wherein the negative phase input end at least connects with a plurality of resistors.
 14. The protective circuit for a motor as defined in claim 7, wherein the negative phase input end at least connects with a plurality of resistors.
 15. The protective circuit for a motor as defined in claim 8, wherein the negative phase input end at least connects with a plurality of resistors.
 16. The protective circuit for a motor as defined in claim 7, wherein the output end at least connects with a plurality of resistors.
 17. The protective circuit for a motor as defined in claim 8, wherein the output end at least connects with a plurality of resistors. 